Numerous tong assemblies exist which are effective to make up and break out a threaded tool joint. However, many of these tongs are complex in design and operation and/or limited with respect to the size range of drill pipe which can be accommodated. Some tongs grip a tool joint at only two locations, increasing the potential for slipping of the joint from the grip of the jaw dies, and for wear of the dies, as well as the potential for overstressing of the tool joint. Other tongs alleviate these limitations through the use of three or more movable jaws and associated gripping dies. Exemplary of this type of tong is that described in U.S. Pat. No. 4,005,621, assigned to the assignee of the instant invention, which teaches the simultaneous camming engagement of preferably three jaw dies with a tool joint whereby equal forces are applied to the joint. The patent also teaches a backup tong suspended from a power tong, the backup tong requiring inversion for the respective makeup or break down operation. The power tong and backup tong described in the patent, as with all known tongs, is designed such that during operation the tool joint is positioned with its central axis along the longitudinal axis of the tongs. The tool joint is centered in the primary openings surrounding the tool joint during operation.
It is desirable to provide a tong assembly, including an interconnected power tong and backup tong, wherein the backup tong effectively contacts a tool joint at at least three points, and which allows makeup and break out without inverting the backup tong.